Between April 2015 and April 2019, 155 consecutive patients were treated with GTV to high-risk CTV margin of 10mm and subsequently another 155 patients with 6mm margin. The CTV-PTV margin was 3mm for both groups. All patients were treated with volumetric-modulated arc therapy with daily image-guidance using cone-beam CT. End points of the study were acute and late toxicity and oncologic outcomes.
Overall acute grade 3 toxicity was significantly lower in 6mm, compared to 10mm group (48% vs. 67%, respectively, p<0.01). The same was true for acute grade 3 mucositis (18% vs. 34%, p<0.01) and grade ≥2 dysphagia (67% vs. 85%, p<0.01). Also feeding tube-dependency at the end of treatment (25% vs. 37%, p=0.02), at 3 months (12% and 25%, p<0.01), and at 6 months (6% and 15%, p=0.01) was significantly less in 6mm group. The incidence of late grade 2 xerostomia was also significantly lower in the 6mm group (32% vs. 50%, p<0.01). The 2-year rates of loco-regional control, disease-free and overall survival were 78.7% vs. 73.1%, 70.6% vs. 61.4%, and 83.2% vs. 74.4% (p>0.05, all).
The first study reporting on reduction of GTV to high-risk CTV margin from 10 to 6mm showed significant reduction of the incidence and severity of radiation-related toxicity without reducing local-regional control and survival.
We aim to retrospectively investigate whether reducing GTV to high-risk CTV margin will significantly reduce acute and late toxicity without jeopardizing outcome in head-and-neck squamous cell carcinoma (HNSCC) treated with definitive (chemo)radiation.